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The Forming Process Of Expanded Polytetrafluoroethylene
- May 17, 2018 -

The formation of expanded polytetrafluoroethylene is divided into two stages. In the first stage, PTFE dispersion resin and lubricant additives are mixed in a certain proportion. After a certain time, the preform is preformed, and then the paste is extruded into a longitudinal fiber shaped preform to dry out the auxiliary. The second stage is stretched at a high speed at a temperature below the melting point of polytetrafluoroethylene, and then at a temperature higher than the melting point of the polytetrafluoroethylene semifinished semi-finished product. To expand polytetrafluoroethylene products. The process flow is as follows:

(1) mix the polytetrafluoroethylene resin and the extrusion agent at a certain mass ratio and mix evenly. The dispersion resin has good fibrinolysis, and the cohesion of the particles is low. The molecular chain is arranged along the long axis of the particle by a small shear action, forming a linear crystal. Adding extruding agent can increase adhesion of particles, reduce friction between resin particles and resin and container, and improve machining performance. The extruder is usually available in petroleum ether, toluene, acetone, kerosene, paraffin and so on.

(2) preforms the mixture into a blank body with the same shape as the cavity of the press.

(3) push the pressed body into the membrane cavity of the pushing press and push the bar to obtain the bar.

(4) calendaring roll is used to roll the bar and make the strip with the required width and thickness.

(5) drying and drying the strip and removing the extruding agent on the strip to obtain PTFE film.

(6) expand the PTFE film quickly, and the stretching temperature should be controlled between the glass transition temperature (115 degree) and melting point (327 degree) of PTFE. Because the polymer chain has enough vitality when it is higher than the glass temperature, it can be pulled open, straighten and move to each other. When the temperature is higher than the melting point, the polytetrafluoroethylene particles have melted and become a dense whole, destroying the original fiber bundle folding form of the particles, and it is difficult to be pulled apart.